http://www.dol.gov/whd/regs/compliance/1421.htm
This should answer most of your questions.
I'm sorry your sick. But I'm sure with you missing work and being since is also hard on your boss and other Co workers. I'm not sure what type of job you have. But someone has to cover you when you are gone.
It depends on your state and the type of company you work for. Not everyone is covered under FMLA, regardless of what it says. There are many exceptions. If your company falls under one that is, which is dependant on # of employees, then you also cannot just get time off being sick. FMLA basically says that if your Dr puts you on medical disability, the company cannot fire you or give away your position. This does NOT include random sick days. It has to be longer than 2w straight, again depending on your state and company. The US has the worst pregnancy leave benefits of all major countries, sorry!